A Compact UWB Bandpass Filter using Hybrid Fractal Shaped DGS

Babu lal Shahu, Neela Chattoraj, Srikanta Pal, Dileep Kumar Upadhyay

Abstract

In this paper, a novel compact ultra wideband (UWB) bandpass filter (BPF) based on fractal-shaped defected ground structure is designed and developed with more than -20 dB out-of-band rejection level. It is made of stepped impedance line and composite right/left handed-transmission line (CRLH-TL) constructed with capacitive gap in conductor strip and a hybrid fractal-shaped ring slot in ground plane. The proposed UWB bandpass filter has good passband performance with -10 dB return-loss bandwidth of 2.2 GHz to 10.6 GHz with fractional bandwidth of 131%. The prototype of proposed filter is fabricated and measured. Good agreement is seen between simulated and measured results.Â The designed and developed filter is compact in size, simple in geometry and owns good S-parameters performance characteristics in both passband as well as in stopband. Return-loss better than 10 dB and insertion-loss less than 0.4 dB (except at some higher frequency) is obtained throughout the passband whereas, in stopband, insertion-loss more than 20 dB and return-loss better than 0.8 dB is observed up to the stopband frequency of 20 GHz. Moreover, UWB BPF also shows the flat group delay (variation â‰¤ 0.75 ns) performance. Thus the proposed filter can be a useful candidate for low profile future wireless communication systems.